Marine outdrives using surface piercing propellers have been known and used in the past. Representative disclosures relating to marine outdrives of this type include the following U.S. Pat. Nos. 4,645,463 and 4,909,175.
A marine outdrive with a surface piercing propeller, as set forth in the above disclosures, has a tubular propeller shaft carrier or mount coupled to the transom of a boat by a universal joint in the form of a spherical ball. This construction allows the rotatable propeller at the rear end of the shaft rotatably carried by the mount to be shifted by fluid piston and cylinder assemblies into any one of a number of different attitudes with respect to the boat transom. Thus, the thrust of the marine outdrive itself can be generated and varied as to direction and magnitude, thereby providing great versatility to the outdrive and adapting it for a wide range of speed and other requirements for boats of different sizes.
It has been found through extensive use of a marine outdrive of this type that the propeller itself tends to "walk" across the water from right to left for clockwise rotation (when viewing forwardly) of the propeller and from left to right for counterclockwise rotation of the propeller. This tendency of the propeller shaft mount to "walk" on the water gives rise to unstable forward movements of the boat on which the outdrive is mounted. It also causes the boat to be difficult to handle, especially at high speeds. The constant need to try to keep the steering gear of the boat steady under the adverse conditions caused by the "walking" of the propeller across the water causes fatigue of the operator of the boat over long periods of time. This is especially true with high speed boats which must continuously be steadied to maintain control of the boats. Also, the thrust line of the boat tends to vary relative to the transom which further complicates the operation of the boat and limits its top speed.
Attempts have been made to eliminate this walking of the propeller across the water but such attempts have been generally unsuccessful for one or more reasons. The problem continues to plague suppliers and users of marine outdrives with surface piercing propellers. Accordingly, a need continues to exist for improvements in this area and the present invention satisfies this need by providing several solutions to the problem.